Substrate cleaning apparatus and substrate cleaning method

ABSTRACT

There is provided a substrate cleaning apparatus capable of highly effective self-cleaning of a cleaning tool in a short time period. The substrate cleaning apparatus includes a cleaning tool for cleaning a substrate while in contact with a surface of the substrate, a self-cleaning member for self-cleaning the cleaning tool while in contact with the cleaning tool, a rotation mechanism for rotating the cleaning tool, and a holding mechanism for holding the cleaning tool, the holding mechanism being capable of pressing the cleaning tool against the substrate and pressing the cleaning tool against the self-cleaning member. The substrate cleaning apparatus also includes a controller which controls pressing force for the cleaning tool against the self-cleaning member such that self-cleaning torque, with which the rotation mechanism rotates the cleaning tool at the time of self-cleaning of the cleaning tool, is prescribed torque equal to or more than substrate cleaning torque, with which the rotation mechanism rotates the cleaning tool when the cleaning tool cleans the substrate.

TECHNICAL FIELD

The present invention relates to a substrate cleaning apparatus and asubstrate cleaning method.

BACKGROUND ART

In a manufacturing process of semiconductor devices, various types offilms different in physical properties are formed on a siliconsubstrate, and the films are subjected to various types of processing,thereby forming fine metal wiring. For example, in a damascene wiringformation process, a wiring groove is formed in a film, and a metal,such as Cu, is embedded in the wiring groove. After that, excess metalis removed by chemical mechanical polishing (CMP), thereby forming metalwiring. Generally, a CMP apparatus (polishing apparatus) which polishesa substrate is equipped with a substrate cleaning apparatus which cleansa polished substrate. A substrate is cleaned by bringing a cleaningtool, such as a roll sponge or a pen sponge, into contact with thesubstrate while rotating the substrate.

As cleaning of a substrate with a cleaning tool proceeds, abrasivegrains used in CMP and polishing debris (hereinafter also collectivelyreferred to as “processing debris”) are accumulated on a surface of andin the cleaning tool. In order to remove such processing debris from thecleaning tool, periodic self-cleaning of the cleaning tool is performed.The self-cleaning of the cleaning tool is performed by bringing thecleaning tool into contact with a self-cleaning member, such as a brushor a plate, while rotating the cleaning tool. Before cleaning a polishedsubstrate with a new replacement brush, processing called a break-insimilar to the self-cleaning is also performed for the purpose ofinitializing the brush. The processes will be collectively referred toas self-cleaning hereinafter.

The above-described self-cleaning of a cleaning tool is, for example,performed between substrates (each time one substrate is cleaned) in arelatively short time period and performed between lots (each time aprescribed number of substrates are cleaned) and at the time of break-inprocessing in a relatively long time period. Ultrapure water is oftenused as a cleaning liquid for substrate-to-substrate self-cleaning, anda chemical solution may be used as a cleaning liquid for lot-to-lotself-cleaning and at the time of break-in processing.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laid-Open No. 2005-12238

SUMMARY OF INVENTION Technical Problem

Since self-cleaning of a cleaning tool is executed during a substrateprocessing process or between substrate processing processes, when atime period taken for self-cleaning is longer, the overall timeefficiency of substrate processing decreases. In contrast, when theself-cleaning effect for the cleaning tool is reduced by shortening atime period taken for self-cleaning, processing debris left at thecleaning tool contaminates a substrate.

It is conceivable to adjust a rotational speed of a cleaning tool, atemperature of a cleaning liquid, and the like in order to enhance theself-cleaning effect. That is, increase in the rotational speed of thecleaning tool is assumed to increase the frequency of contact at aportion of contact between the cleaning tool and a self-cleaning memberand enhance the self-cleaning effect for the cleaning tool.Additionally, increase in the temperature of the cleaning liquid isassumed to make polishing debris more likely to be discharged into thecleaning liquid and enhance the self-cleaning effect for the cleaningtool.

The self-cleaning effect is affected by friction between the cleaningtool and the self-cleaning member. When the friction between thecleaning tool and the self-cleaning member is insufficient, processingdebris is not discharged from the cleaning tool, and a fullself-cleaning effect is not achieved. In contrast, excessive frictionbetween the cleaning tool and the self-cleaning member can causeabrasion and deterioration of the cleaning tool. As a result of studiesby the present inventor, it has found that a press and a rotationalspeed of a cleaning tool and a temperature of a cleaning liquid affectfriction between the cleaning tool and a self-cleaning member in variousmanners.

An object of the present invention, which has been made in view of atleast a part of the above-described problems, is to provide a substratecleaning apparatus or a substrate cleaning method capable of highlyeffective self-cleaning of a cleaning tool in a short time period.Another object of the present invention is to provide a substratecleaning apparatus or a substrate cleaning method capable ofself-cleaning of cleaning tool by pressing the cleaning tool against aself-cleaning member with suitable pressing force.

Solution to Problem

(Mode 1) According to mode 1, there is proposed a substrate cleaningapparatus. The substrate cleaning apparatus includes a cleaning tool forcleaning a substrate while in contact with a surface of the substrate, aself-cleaning member for self-cleaning the cleaning tool while incontact with the cleaning tool, a rotation mechanism for rotating thecleaning tool, a holding mechanism which holds the cleaning tool, theholding mechanism being capable of pressing the cleaning tool againstthe substrate and pressing the cleaning tool against the self-cleaningmember, and a controller which controls pressing force for the cleaningtool against the self-cleaning member such that torque, with which therotation mechanism rotates the cleaning tool when the cleaning tool isin contact with the self-cleaning member, is prescribed torque equal toor more than substrate cleaning torque, with which the rotationmechanism rotates the cleaning tool when the cleaning tool cleans thesubstrate. According to mode 1, it is possible to press the cleaningtool against the self-cleaning member with suitable pressing force andself-clean the cleaning tool.

(Mode 2) According to mode 2, there is proposed a substrate cleaningapparatus. The substrate cleaning apparatus includes a cleaning tool forcleaning a substrate while in contact with a surface of the substrate, aself-cleaning member for self-cleaning the cleaning tool while incontact with the cleaning tool, a rotation mechanism for rotating thecleaning tool, a holding mechanism which holds the cleaning tool, theholding mechanism being capable of pressing the cleaning tool againstthe substrate and pressing the cleaning tool against the self-cleaningmember, and a controller which, when the cleaning tool is in contactwith the self-cleaning member, controls the holding mechanism such thatthe cleaning tool is pressed against the self-cleaning member with firstpressing force when the cleaning tool is rotating at a first rotationalspeed and controls the holding mechanism such that the cleaning tool ispressed against the self-cleaning member with second pressing forcelarger than the first pressing force when the cleaning tool is rotatingat a second rotational speed higher than the first rotational speed.Mode 2 is based on the discovery that friction between the cleaning tooland the self-cleaning member tends to decrease with increase in arotational speed of the cleaning tool. According to mode 2, it ispossible to press the cleaning tool against the self-cleaning memberwith suitable pressing force and self-clean the cleaning tool.

(Mode 3) According to mode 3, there is proposed a substrate cleaningapparatus. The substrate cleaning apparatus includes a cleaning tool forcleaning a substrate while in contact with a surface of the substrate, aself-cleaning member for self-cleaning the cleaning tool while incontact with the cleaning tool, a rotation mechanism for rotating thecleaning tool, a holding mechanism which holds the cleaning tool, theholding mechanism being capable of pressing the cleaning tool againstthe substrate and pressing the cleaning tool against the self-cleaningmember, and a controller which, when the cleaning tool is in contactwith the self-cleaning member in liquid or with supply of the liquid,controls the holding mechanism such that the cleaning tool is pressedagainst the self-cleaning member with first pressing force when theliquid is at a first temperature and controls the holding mechanism suchthat the cleaning tool is pressed against the self-cleaning member withsecond pressing force larger than the first pressing force when theliquid is at a second temperature higher than the first temperature.Mode 3 is based on the discovery that friction between the cleaning tooland the self-cleaning member decreases with increase in a temperature ofthe liquid used for self-cleaning. According to mode 3, it is possibleto press the cleaning tool against the self-cleaning member withsuitable pressing force and self-clean the cleaning tool.

(Mode 4) According to mode 4, there is proposed a substrate cleaningapparatus. The substrate cleaning apparatus includes a cleaning tool forcleaning a substrate while in contact with a surface of the substrate, afirst self-cleaning member for self-cleaning the cleaning tool while incontact with the cleaning tool, the first self-cleaning member beingformed of a first material, and a second self-cleaning member forself-cleaning the cleaning tool while in contact with the cleaning tool,the second self-cleaning member being formed of a second material, andselects one of the first self-cleaning member and the secondself-cleaning member on the basis of external input and self-cleans thecleaning tool by bringing the cleaning tool into contact with theselected self-cleaning member. According to mode 4, it is possible toselect the self-cleaning member on the basis of the external input andself-clean the cleaning tool. This allows highly effective self-cleaningof the cleaning tool in a short time period.

(Mode 5) According to mode 5, there is proposed a substrate cleaningapparatus. The substrate cleaning apparatus includes a cleaning tool forcleaning a substrate while in contact with a surface of the substrate, afirst self-cleaning member for self-cleaning the cleaning tool while incontact with the cleaning tool, the first self-cleaning member beingformed of a first material, and a second self-cleaning member forself-cleaning the cleaning tool while in contact with the cleaning tool,the second self-cleaning member being formed of a second material, andself-cleans the cleaning tool by bringing the cleaning tool into contactwith the first self-cleaning member and then bringing the cleaning toolinto contact with the second self-cleaning member. According to mode 5,self-cleaning of the cleaning tool is performed using the twoself-cleaning members. This allows enhancement of a self-cleaning effectfor the cleaning tool.

(Mode 6) According to mode 6, in the substrate cleaning apparatus ofmode 4 or 5, the first material is a material in which surface freeenergy has a larger hydrogen-bonding component and a smaller dispersionforce component than the second material at the time of self-cleaningthe cleaning tool. According to mode 6, it is possible to first removeprocessing debris, such as abrasive grains, in which surface free energyhas a larger hydrogen-bonding component from the cleaning tool, usingthe first self-cleaning member and then remove processing debris, suchas organic complexes, in which surface free energy has a largerdispersion force component from the cleaning tool, using the secondself-cleaning member.

(Mode 7) According to mode 7, in the substrate cleaning apparatus ofanyone of modes 4 to 6, the first material is an inorganic oxide-basedmaterial or a first organic polymer-based material which has a polargroup in a molecular structure, and the second material is a secondorganic polymer-based material which is non-polar.

(Mode 8) According to mode 8, in the substrate cleaning apparatus ofanyone of modes 1 to 7, the self-cleaning of the cleaning tool includesshort-time self-cleaning of first duration and long-time self-cleaningof second duration longer than the first duration, and ultrapure wateris used in the short-time self-cleaning, and a chemical solution may beused in the long-time self-cleaning, and ultrapure water-based rinseprocessing is subsequently performed when a chemical solution is used.In either case, a cleaning effect may be enhanced by increasing a liquidtemperature. Note that, when rinsing using ultrapure water is performedafter use of a chemical solution, cleaning torque may change before orafter the rinsing. In the case, pressing or the number of revolutions isadjusted such that the cleaning torque is equal to or more than torqueat the time of wafer cleaning.

(Mode 9) According to mode 9, the substrate cleaning apparatus of anyoneof modes 1 to 8 further includes a bath in which liquid is stored andwhich houses the self-cleaning member, and a vibration module whichgives ultrasound vibration to the liquid.

(Mode 10) According to mode 10, the substrate cleaning apparatus ofanyone of modes 1 to 9 further includes a jetting module which jets gasor liquid toward the cleaning tool when the cleaning tool isself-cleaned.

(Mode 11) According to mode 11, there is proposed a substrate cleaningmethod. The substrate cleaning method includes a cleaning step ofcleaning a substrate by rotating a cleaning tool and bringing thecleaning tool into contact with a surface of the substrate, and aself-cleaning step of self-cleaning the cleaning tool by rotating thecleaning tool and bringing the cleaning tool into contact with aself-cleaning member, and the self-cleaning step includes controllingpressing force for the cleaning tool against the self-cleaning membersuch that torque which rotates the cleaning tool is prescribed torqueequal to or more than substrate cleaning torque which rotates thecleaning tool in the cleaning step. According to mode 11, it is possibleto press the cleaning tool against the self-cleaning member withsuitable pressing force and self-clean the cleaning tool.

(Mode 12) According to mode 12, there is proposed a substrate cleaningmethod. The substrate cleaning method includes a cleaning step ofcleaning a substrate by rotating a cleaning tool and bringing thecleaning tool into contact with a surface of the substrate, and aself-cleaning step of self-cleaning the cleaning tool by rotating thecleaning tool and bringing the cleaning tool into contact with aself-cleaning member, and the self-cleaning step includes pressing thecleaning tool against the self-cleaning member with first pressing forcewhen the cleaning tool is rotating at a first rotational speed andpressing the cleaning tool against the self-cleaning member with secondpressing force larger than the first pressing force when the cleaningtool is rotating at a second rotational speed higher than the firstrotational speed. According to mode 12, it is possible to press thecleaning tool against the self-cleaning member with suitable pressingforce and self-clean the cleaning tool.

(Mode 13) According to mode 13, there is proposed a substrate cleaningmethod. The substrate cleaning method includes a cleaning step ofcleaning a substrate by rotating a cleaning tool and bringing thecleaning tool into contact with a surface of the substrate, and aself-cleaning step of self-cleaning the cleaning tool by rotating thecleaning tool and bringing the cleaning tool into contact with anin-bath self-cleaning member in liquid or with supply of the liquid, andthe self-cleaning step includes pressing the cleaning tool against theself-cleaning member with first pressing force when the liquid is at afirst temperature and pressing the cleaning tool against theself-cleaning member with second pressing force larger than the firstpressing force when the liquid is at a second temperature higher thanthe first temperature. According to mode 13, it is possible to press thecleaning tool against the self-cleaning member with suitable pressingforce and self-clean the cleaning tool.

(Mode 14) According to mode 14, there is proposed a substrate cleaningmethod. The substrate cleaning method includes a cleaning step ofcleaning a substrate by rotating a cleaning tool and bringing thecleaning tool into contact with a surface of the substrate, a selectionstep of selecting one of a first self-cleaning member which is formed ofa first material and a second self-cleaning member which is formed of asecond material, on the basis of external input, and a self-cleaningstep of self-cleaning the cleaning tool by rotating the cleaning tooland bringing the cleaning tool into contact with the self-cleaningmember selected in the selection step. According to mode 14, it ispossible to select the self-cleaning member on the basis of the externalinput and self-clean the cleaning tool. This allows highly effectiveself-cleaning of the cleaning tool in a short time period.

(Mode 15) According to mode 15, there is proposed a substrate cleaningmethod. The substrate cleaning method includes a cleaning step ofcleaning a substrate by rotating a cleaning tool and bringing thecleaning tool into contact with a surface of the substrate, a firstself-cleaning step of self-cleaning the cleaning tool by rotating thecleaning tool and bringing the cleaning tool into contact with a firstself-cleaning member which is formed of a first material, and a secondself-cleaning step of, after the first self-cleaning step, self-cleaningthe cleaning tool by rotating the cleaning tool and bringing thecleaning tool into contact with a second self-cleaning member which isformed of a second material. According to mode 15, self-cleaning of thecleaning tool is performed using the two self-cleaning members. Thisallows enhancement of a self-cleaning effect for the cleaning tool.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view showing a schematic configuration of a substrateprocessing apparatus including a substrate cleaning apparatus accordingto an embodiment;

FIG. 2 is a perspective view showing a schematic configuration of thesubstrate cleaning apparatus according to the embodiment;

FIG. 3 is a perspective view showing a schematic configuration of asubstrate cleaning apparatus according to another example;

FIG. 4 is a view schematically showing self-cleaning of a pen member;

FIG. 5 is a view schematically showing self-cleaning of a roll member;

FIG. 6 is a flowchart showing an example of a self-cleaning targetpressing force setting process to be executed by a controller accordingto a first embodiment;

FIG. 7 is a flowchart showing an example of a self-cleaning targetpressing force setting process to be executed by a controller accordingto a second embodiment;

FIG. 8 is a graph showing an example of a relationship between a numberNs of revolutions and a temperature Tc, and target pressing force Pp*;

FIG. 9 is a view showing an example of a combination of a bath and aself-cleaning member according to a third embodiment;

FIG. 10 is a flowchart showing an example of a self-cleaning memberselection process to be executed by a controller according to the thirdembodiment; and

FIG. 11 is a flowchart showing an example of a self-cleaning process tobe executed by a controller according to a fourth embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings. In the drawings to be described below, thesame or corresponding components are denoted by the same referencenumerals, and a redundant description thereof will be omitted. Substratecleaning apparatuses according to the embodiments of the presentinvention can each be used as a part of a substrate processing apparatuswhich processes a substrate, such as a semiconductor wafer.

First Embodiment

FIG. 1 is a view showing a schematic configuration of a substrateprocessing apparatus including a substrate cleaning apparatus accordingto an embodiment. As shown in FIG. 1, a substrate processing apparatus10 has a housing 110 and a load port 112 which is arranged adjacent tothe housing 110. An open cassette for stocking many substrates Wf (see,e.g., FIG. 2), a SMIF (Standard Manufacturing Interface) pod, or a FOUP(Front Opening Unified Pod) can be loaded onto the load port 112. A SMIFpod and a FOUP are each an airtight container which houses a substratecassette inside and can maintain an environment independent of anexternal space.

A plurality of (four in the aspect shown in FIG. 1) polishing modules114 a to 114 d, a first cleaning module 116 and a second cleaning module118 which clean the substrate Wf after polishing, and a drying module120 which dries the substrate Wf after cleaning are housed in thehousing 110. In the example shown in FIG. 1, the polishing modules 114 ato 114 d are arrayed in a longitudinal direction of the substrateprocessing apparatus 10, and the cleaning modules 116 and 118 and thedrying module 120 are arranged in parallel with the polishing modules114 a to 114 d.

A first transfer robot 122 is arranged between the load port 112, andthe polishing module 114 a and the drying module 120 located closer tothe load port 112. A transfer module 124 is arranged between thepolishing modules 114 a to 114 d, and the cleaning modules 116 and 118and the drying module 120. The first transfer robot 122 receives thesubstrate Wf before polishing from the load port 112 and passes thesubstrate Wf to the transfer module 124 or receives, from the transfermodule 124, the substrate Wf after drying taken out from the dryingmodule 120.

The polishing modules 114 a to 114 d are each a region where polishing(planarization) of the substrate Wf is performed. Since the polishingmodules 114 a to 114 d are not central to the present invention, adetailed description thereof will be omitted.

A second transfer robot 126 which performs passing of the substrate Wfbetween the first cleaning module 116 and the second cleaning module 118is arranged between the first cleaning module 116 and the secondcleaning module 118. A third transfer module 128 which performs passingof the substrate Wf between the second cleaning module 118 and thedrying module 120 is arranged between the second cleaning module 118 andthe drying module 120. Additionally, a controller 50 which controls themovement of the modules of the substrate processing apparatus 10 isarranged inside the housing 110. In the present embodiment, thecontroller 50 is arranged inside the housing 110. Note that the presentinvention is not limited to this example and that the controller 50 maybe arranged outside the housing 110. In the present embodiment, thecontroller 50 has an input module 52 which accepts external input. Theexternal input here can include a user's mechanical operation and wiredor wireless signal input from an external device.

The cleaning modules 116 and 118 according to the present embodimenteach clean the substrate Wf by bringing a cleaning tool (to be describedlater) into contact with the surface of the substrate Wf while causingthe cleaning tool to rotate. As each of the cleaning modules 116 and118, a two-fluid jet cleaning device which cleans the surface of thesubstrate Wf with a two-fluid jet may be used in combination with thecleaning tool.

By way of example, the drying module 120 dries the substrate Wf byjetting IPA steam from a nozzle (not shown) toward the rotatingsubstrate Wf. Alternatively, the drying module 120 may rotate thesubstrate Wf at high speed and dry the substrate Wf by centrifugalforce.

FIG. 2 is a perspective view showing a schematic configuration of asubstrate cleaning apparatus according to the embodiment, and FIG. 3 isa perspective view showing a schematic configuration of a substratecleaning apparatus according to another example. As shown in FIGS. 2 and3, a substrate cleaning apparatus 20 (the cleaning module 116 or 118)has a substrate rotation mechanism (see support members 40 (to bedescribed later) in the present embodiment) which hold and rotate thesubstrate Wf and supply modules 42 which supply a cleaning liquid to thesubstrate Wf. Cleaning liquids according to the present embodimentinclude a rinse solution, such as ultrapure water (DIW), and a chemicalsolution, such as an aqueous solution of ammonia and hydrogen peroxide(SC-1), an aqueous solution of hydrochloric acid and hydrogen peroxide(SC-2), an aqueous solution of sulfuric acid and hydrogen peroxide(SPM), or hydrofluoric acid. Unless otherwise noted in the presentembodiment, a cleaning liquid refers to either a rinse solution or achemical solution.

The substrate Wf rotates on its central axis (an axis passing through acenter O and perpendicular to the surface of the substrate Wf) as arotation axis. Although the present embodiment will be described mainlyusing an aspect in which the surface of the substrate Wf extends along ahorizontal direction and the rotation axis extends in a verticaldirection, the present invention is not limited to this. The substraterotation mechanism according to the present embodiment has four supportmembers 40 which support an outer perimeter of the substrate Wf. Thesupport member 40 is, for example, a spindle, a chuck, or the like.Rotation of the spindle, chuck, or the like allows rotation of thesubstrate Wf.

The substrate cleaning apparatus 20 includes a cleaning tool 11 whichcleans the substrate Wf while in contact with the substrate Wf, arotation mechanism 31 which rotates the cleaning tool 11, and a holdingmechanism 32 which holds the cleaning tool 11. A pen member 11A (seeFIG. 2) which rotates about a rotation axis generally perpendicular tothe surface of the substrate Wf can be used as the cleaning tool 11.Alternatively, a roll member 11B (see FIGS. 2 and 3) which extendslinearly over almost the entire length of a diameter of the substrate Wfcan be used as the cleaning tool 11.

The rotation mechanism 31 rotates the cleaning tool 11 about a rotationaxis generally perpendicular to the surface of the substrate Wf when thepen member 11A is used as the cleaning tool 11. The rotation mechanism31 rotates the cleaning tool 11 about a rotation axis parallel to thesurface of the substrate Wf when the roll member 11B is used as thecleaning tool 11. Various types of mechanisms can be adopted as therotation mechanism 31. By way of example, a DC motor and a linkmechanism can be adopted.

The holding mechanism 32 can move the cleaning tool 11 and the rotationmechanism 31 perpendicularly to the surface of the substrate Wf andpress the cleaning tool 11 against the substrate Wf or move the cleaningtool 11 away from the substrate Wf. Various types of mechanisms can beadopted as the holding mechanism 32. By way of example, a motor drivemechanism using a ball screw, an air cylinder, or the like can beadopted. Alternatively, the holding mechanism 32 can move the cleaningtool 11 and the rotation mechanism 31 parallel to the surface of thesubstrate Wf and change a portion of contact between the cleaning tool11 and the substrate Wf or move the cleaning tool 11 to a standbyposition (not shown).

Note that, in the example shown in FIG. 2, the pen member 11A cleans anupper surface (an upper surface in FIG. 2) of the substrate Wf and thatthe roll member 11B cleans a lower surface (a lower surface in FIG. 2)of the substrate Wf. In the example shown in FIG. 3, the roll member 11Bcleans the obverse and the reverse of the substrate Wf. Note that thesubstrate Wf only needs to be cleaned by the cleaning tool 11 in contactwith the surface of the substrate Wf and that the substrate cleaningapparatus 20 is not limited to the example in FIG. 2 or 3.

In a case where a new cleaning tool 11 is used (e.g., the cleaning tool11 is replaced with another), a break-in of the cleaning tool 11 isperformed. Since the cleaning tool 11 may be dry in its initial state,the cleaning tool 11 may damage the substrate Wf when the cleaning tool11 in this state is used for cleaning processing. Even when the cleaningtool 11 is provided in a wet state, particles which are a source ofcontamination may be adherent to a sponge itself. For this reason, thecleaning tool 11 is saturated with water and is kneaded or an initialwarm-up (break-in) is performed to remove the particles. Cleaningprocessing is executed using the cleaning tool 11 having undergone thebreak-in, and the substrate Wf is checked for back contamination aftercleaning. Back contamination means that the clean substrate Wf iscontaminated by the cleaning tool 11. Since occurrence of backcontamination has a significant adverse effect on subsequent processes,a checkup for back contamination is important.

As cleaning of the substrate Wf with the cleaning tool 11 proceeds,processing debris at the time of polishing of the substrate Wf isaccumulated on the surface of and in the cleaning tool 11. For thisreason, self-cleaning of the cleaning tool 11 is periodically performed.The self-cleaning is performed by bringing the cleaning tool 11 intocontact with a self-cleaning member 60. The self-cleaning of thecleaning tool 11 is performed between substrates (each time onesubstrate is cleaned) in a relatively short time period (a first timeperiod) and performed between lots (each time a prescribed number ofsubstrates are cleaned) in a relatively long time period (a second timeperiod). In the present embodiment, in substrate-to-substrateself-cleaning, pure water (DIW) or the like is used as a liquid to beused for self-cleaning. In contrast, in lot-to-lot self-cleaning,ultrapure water is used after a chemical solution, such as an aqueoussolution of ammonia and hydrogen peroxide (SC-1), an aqueous solution ofhydrochloric acid and hydrogen peroxide (SC-2), an aqueous solution ofsulfuric acid and hydrogen peroxide (SPM), or hydrofluoric acid, isused. Note that the present invention is not limited to this example, achemical solution may be used in substrate-to-substrate self-cleaning,and that a chemical solution may not be used in lot-to-lotself-cleaning. Note that self-cleaning is assumed to include a break-inin the following description.

FIG. 4 is a view schematically showing self-cleaning of the pen member11A, and FIG. 5 is a view schematically showing self-cleaning of theroll member 11B. As shown in FIGS. 4 and 5, the self-cleaning member 60is arranged in a bath 62. The self-cleaning member 60 is formed of forexample, an inorganic oxide-based material, such as a quartz plate or asapphire plate, or a good organic polymer-based material with chemicalresistance and low elution, such as PTFE, PVDF, PFA, PPS, PEEK, or PMMA.A liquid 64, such as ultrapure water (DIW) or a chemical solution (e.g.,an aqueous solution of ammonia and hydrogen peroxide (SC-1), an aqueoussolution of hydrochloric acid and hydrogen peroxide (SC-2), an aqueoussolution of sulfuric acid and hydrogen peroxide (SPM), or hydrofluoricacid), is stored in the bath 62. In the bath 62, it is preferable that atransport mechanism 65 supply a clean liquid or circulate an internalliquid while cleaning the internal liquid. The liquid 64 stored in thebath 62 is preferably adjusted in temperature by an adjustment mechanism66. For example, a heater can be used as the adjustment mechanism 66.Additionally, the substrate cleaning apparatus 20 may include avibration module 67 which gives ultrasound vibration into the bath 62 atthe time of self-cleaning of the cleaning tool 11. Alternatively, thesubstrate cleaning apparatus 20 may include a jetting module 68 whichjets gas or liquid toward the cleaning tool 11 at the time ofself-cleaning of the cleaning tool 11.

Note that the self-cleaning member 60 is arranged in the bath 62 in theexamples shown in FIGS. 4 and 5. The present invention, however, is notlimited to these examples, and the bath 62 may not be provided. Notethat, even when the bath 62 is not provided, self-cleaning of thecleaning tool 11 may be performed with supply of the liquid 64 by thetransport mechanism 65, i.e., while the liquid 64 is, for example,continuously run over the cleaning tool 11. Even in this case, atemperature of the liquid 64 may be adjusted by the adjustment mechanism66.

As shown in FIG. 4, when the pen member 11A is self-cleaned, therotation mechanism 31 rotates the pen member 11A, and the holdingmechanism 32 presses the pen member 11A against the self-cleaning member60. Note that although FIG. 4 shows an example where a surface of theself-cleaning member 60 is perpendicular to the rotation axis of the penmember 11A, the present invention is not limited to this example. Asshown in FIG. 5, when the roll member 11B is self-cleaned, the rotationmechanism 31 rotates the roll member 11B, and the holding mechanism 32presses the roll member 11B against the self-cleaning member 60. Notethat although, in the example shown in FIG. 5, the surface of theself-cleaning member 60 is inclined to the vertical direction, and theroll member 11B moves in the vertical direction to come into contactwith the self-cleaning member 60, the present invention is not limitedto this example.

FIG. 6 is a flowchart showing an example of a self-cleaning targetpressing force setting process to be executed by the controller 50according to the embodiment. This process is executed at prescribed timeintervals (e.g., every several tens of msec) when the cleaning tool 11is brought into contact with the self-cleaning member 60, i.e., when thecleaning tool 11 is self-cleaned.

When the above-described process is started, the controller 50 firstreads output torque Tr from the rotation mechanism 31 (S12). The outputtorque Tr is torque, with which the rotation mechanism 31 rotates thecleaning tool 11, when the cleaning tool 11 and the self-cleaning member60 are in contact and can be detected on the basis of, for example, avalue of current which flows to a motor (not shown) of the rotationmechanism 31. As for the output torque Tr, a torque command from thecontroller 50 to the rotation mechanism 31 may be used.

The controller 50 then sets target pressing force Pp*, with which thecleaning tool 11 is to be pressed against the self-cleaning member 60,on the basis of the output torque Tr and prescribed target torque Tr*(S14) and ends the present process. The target torque Tr* here isprescribed torque determined in advance and is torque equal to or morethan torque (substrate cleaning torque) which acts on the cleaning tool11 when the cleaning tool 11 cleans the substrate Wf. The target torqueTr* may be set by external input. By way of example, the setting of thetarget pressing force Pp* can be performed on the basis of a differencebetween the output torque Tr and the target torque Tr* by a PI operationusing a proportional gain Gp and an integral gain Gi or a PID operationusing the proportional gain Gp, the integral gain Gi, and a derivativegain Gd. When the controller 50 ends the present process, the controller50 controls the holding mechanism 32 such that the cleaning tool 11 ispressed against the self-cleaning member 60 with the target pressingforce Pp*.

Friction between the cleaning tool 11 and the self-cleaning member 60varies with not only pressing force Pp for the cleaning tool 11 againstthe self-cleaning member 60 but also conditions, such as abrasion of thecleaning tool 11, a rotational speed (a number Ns of revolutions) of thecleaning tool 11, a type and a temperature Tc of the liquid 64, and amaterial for and a shape of the self-cleaning member 60. When thefriction between the cleaning tool 11 and the self-cleaning member 60 isinsufficient, a full self-cleaning effect may not be achieved inself-cleaning of the cleaning tool 11. In this case, the insufficientself-cleaning of the cleaning tool 11 may cause back contamination ofthe substrate Wf to adversely affect subsequent processes or increase atime period and a cost required for a break-in checkup. On the otherhand, when the friction between the cleaning tool 11 and theself-cleaning member 60 is excessively large, abrasion may causedeterioration of the cleaning tool 11. In contrast, in the substratecleaning apparatus 20 according to the present embodiment, pressingforce for the cleaning tool 11 against the self-cleaning member 60 iscontrolled such that the output torque Tr from the rotation mechanism 31when the cleaning tool 11 and the self-cleaning member 60 are in contactis the prescribed torque equal to or more than the substrate cleaningtorque. Adoption of torque which prevents deterioration of the cleaningtool 11 as the prescribed torque makes it possible to press the cleaningtool 11 against the self-cleaning member 60 with suitable pressing forceand self-clean the cleaning tool 11.

In the substrate cleaning apparatus 20 according to the presentembodiment, the target torque Tr* is set at torque equal to or more thanthe substrate cleaning torque. That is, the target torque Tr* is torqueequal to or more than torque which acts on the cleaning tool 11 whenprocessing debris is accumulated at the cleaning tool 11. Use of thetarget torque Tr* makes it possible to suitably remove processing debrisfrom the cleaning tool 11 in a short time period.

Second Embodiment

A substrate processing apparatus 10 according to a second embodiment hasthe same configuration as the substrate processing apparatus 10according to the first embodiment, and a redundant description thereofwill be omitted. The substrate processing apparatus 10 according to thesecond embodiment is different from the substrate processing apparatus10 according to the first embodiment in that a self-cleaning targetpressing force setting process shown in FIG. 7 is executed instead ofthe process shown in FIG. 6. The process shown in FIG. 7 is executed atprescribed time intervals (e.g., every several tens of msec) by acontroller 50 when a cleaning tool 11 is brought into contact with aself-cleaning member 60, i.e., when the cleaning tool 11 isself-cleaned.

When the above-described process is started, a controller 50 reads anumber Ns of revolutions of the cleaning tool 11 and a temperature Tc ofa liquid 64 (S22). As the number Ns of revolutions of the cleaning tool11, a detected value from a sensor (not shown) which detects the numberNs of revolutions of the cleaning tool 11 or a detected value from asensor (not shown) which detects the number of revolutions of a rotationmechanism 31 can be used. As for the number Ns of revolutions of thecleaning tool 11, a number-of-revolutions command to the rotationmechanism 31 may be used. As the temperature Tc of the liquid 64, adetected value from a temperature sensor (not shown) which is providedat a bath 62 can be used. As for the temperature Tc of the liquid 64, atemperature command from an adjustment mechanism 66 may be used.

The controller 50 then sets target pressing force Pp*, with which thecleaning tool 11 is to be pressed against the self-cleaning member 60,on the basis of the number Ns of revolutions and the temperature Tc(S24) and ends the present process. In the process in S24, the targetpressing force Pp* is set such that the target pressing force Pp* tendsto increase with increase in the number Ns of revolutions and tends toincrease with increase in the temperature Tc of the liquid 64. FIG. 8 isa graph showing an example of a relationship between the number Ns ofrevolutions and the temperature Tc, and the target pressing force Pp*.Note that although FIG. 8 shows an example where the target pressingforce Pp* increases linearly with increase in the number Ns ofrevolutions or the temperature Tc, the present invention is not limitedto this example. For example, the target pressing force Pp* may increasein a stepwise manner with increase in the number Ns of revolutions orthe temperature Tc or the relationship between the number Ns ofrevolutions and the temperature Tc, and the target pressing force Pp*may be curvilinearly indicated. By way of example, the relationshipbetween the number Ns of revolutions and the temperature Tc, and thetarget pressing force Pp* can be defined in advance as a map through,e.g., an experiment, and the process in S24 can be performed on thebasis of the map and the number Ns of revolutions and the temperature Tcthat are read. Note that the present invention is not limited to thisexample and that the controller 50 may set the target pressing force Pp*on the basis of the number Ns of revolutions and the temperature Tc byvarious types of methods. When the controller 50 ends the presentprocess, the controller 50 controls a holding mechanism 32 such that thecleaning tool 11 is pressed against the self-cleaning member 60 with thetarget pressing force Pp*.

The studies by the present inventor have discovered that frictionbetween the cleaning tool 11 and the self-cleaning member 60 tends todecrease with increase in the number Ns of revolutions of the cleaningtool 11. For this reason, in a substrate cleaning apparatus 20 accordingto the second embodiment, the cleaning tool 11 is pressed against theself-cleaning member 60 with first pressing force Pp1 when the cleaningtool 11 is rotating at a first rotational speed Ns1. The cleaning tool11 is pressed against the self-cleaning member 60 with second pressingforce Pp2 (Pp2>Pp1) larger than the first pressing force Pp1 when thecleaning tool 11 is rotating at a second rotational speed Ns2 (Ns2>Ns1)higher than the first rotational speed Ns1. This allows inhibition of asituation where a full effect cannot be obtained due to insufficientfriction between the cleaning tool 11 and the self-cleaning member 60when the number Ns of revolutions of the cleaning tool 11 is large. Thatis, the substrate cleaning apparatus 20 according to the secondembodiment can press the cleaning tool 11 against the self-cleaningmember 60 with suitable pressing force and self-clean the cleaning tool11.

The studies by the present inventor have discovered that frictionbetween the cleaning tool 11 and the self-cleaning member 60 tends todecrease with increase in the temperature T of the liquid 64. For thisreason, in the substrate cleaning apparatus 20 according to the secondembodiment, the cleaning tool 11 is pressed against the self-cleaningmember 60 with the first pressing force Pp1 when the temperature Tc ofthe liquid 64 is a first temperature Tc1. The cleaning tool 11 ispressed against the self-cleaning member 60 with the second pressingforce Pp2 (Pp2>Pp1) larger than the first pressing force Pp1 when thetemperature Tc of the liquid 64 is a second temperature Tc2 (Tc2>Tc1)higher than the first temperature Tc1. This allows inhibition of asituation where a full effect cannot be obtained due to insufficientfriction between the cleaning tool 11 and the self-cleaning member 60when the temperature Tc of the liquid 64 is high. That is, the substratecleaning apparatus 20 according to the second embodiment can press thecleaning tool 11 against the self-cleaning member 60 with suitablepressing force and self-clean the cleaning tool 11.

Note that although the target pressing force Pp* is set on the basis ofthe number Ns of revolutions of the cleaning tool 11 and the temperatureTc of the liquid 64 in the substrate cleaning apparatus 20 according tothe second embodiment, the target pressing force Pp* may be set on thebasis of one of the number Ns of revolutions and the temperature Tc. Thetarget pressing force Pp* may be set on the basis of another parameterinstead of or in addition to these parameters. By way of example, thetarget pressing force Pp* may be set so as to increase with increase inthe number of times the substrate Wf is cleaned by the cleaning tool 11.Alternatively, the target pressing force Pp* may be set at a valuelarger when a chemical solution containing a surfactant is used as theliquid 64 than when ultrapure water is used as the liquid 64.Alternatively, the target pressing force Pp* may be set on the basis ofa material for the self-cleaning member 60. Alternatively, the targetpressing force Pp* may be set so as to increase or decrease withincrease in a time period of contact between the cleaning tool 11 andthe self-cleaning member 60.

Third Embodiment

A substrate cleaning apparatus 20 according to a third embodiment isdifferent from the substrate cleaning apparatus 20 according to thefirst embodiment in that the substrate cleaning apparatus 20 has, as aself-cleaning member 60, a first member (a first self-cleaning member)60A which is formed of a first material and a second member (a secondself-cleaning member) 60B which is formed of a second material, and theother components are the same as those of the substrate cleaningapparatus 20 according to the first embodiment. The first material hereis, for example, an inorganic oxide-based material or an organicpolymer-based material (a first organic polymer-based material) in whichsurface free energy has a relatively large hydrogen-bonding componentdue to the presence of a polar group in a molecular structure. Thesecond material is, for example, an organic polymer-based material (asecond organic polymer-based material) in which surface free energy hasa relatively large dispersion force component due to the absence of apolar group in a molecular structure.

FIG. 9 is a view showing an example of a combination of a bath and aself-cleaning member according to the third embodiment. As shown in FIG.9, in the third embodiment, the first member 60A and the second member60B are arranged in a bath 62. Note that the present invention is notlimited to this example, the first member 60A and the second member 60Bmay be arranged in separate baths 62. Alternatively, the bath 62 may notbe provided. Note that, even when the bath 62 is not provided,self-cleaning of a cleaning tool 11 may be performed with supply of aliquid 64 by a transport mechanism 65, i.e., while the liquid 64 is, forexample, continuously run over the cleaning tool 11.

FIG. 10 is a flowchart showing an example of a self-cleaning memberselection process to be executed by a controller 50 according to thethird embodiment. By way of example, the process is executed uponactivation of the substrate cleaning apparatus 20 or at a time when aninput module 52 receives external input. When the present process isexecuted, the controller 50 judges on the basis of the external inputwhether the first member 60A is selected (S42). By way of example, thisprocess can be performed by referring to a prescribed region of a memory(not shown) of the controller 50. When the first member 60A is selected(YES in S42), the controller 50 sets the first member 60A as aself-cleaning member and ends the present process. On the other hand,when the first member 60A is not selected (NO in S42), the controller 50sets the second member 60B as the self-cleaning member and ends thepresent process. The controller 50 executes self-cleaning of thecleaning tool 11 using the self-cleaning member 60 selected by thepresent process.

Suitable materials for the self-cleaning member 60 that self-cleans thecleaning tool 11 are assumed to differ depending on processing debrisaccumulated at the cleaning tool 11. For example, when the self-cleaningmember 60 is intended for processing debris, such as abrasive grains, inwhich surface free energy has a larger hydrogen-bonding component, it isconsidered preferable to use, as the self-cleaning member 60, the firstmember 60A that is formed of an inorganic oxide-based material or anorganic polymer-based material having a polar group in a molecularstructure. When the self-cleaning member 60 is intended for processingdebris, such as organic complexes, in which surface free energy has alarger dispersion force component, it is considered preferable to use,as the self-cleaning member 60, the second member 60B that is formed ofan organic polymer-based material having no polar group in a molecularstructure. To this end, the substrate cleaning apparatus 20 according tothe third embodiment selects the self-cleaning member 60 on the basis ofexternal input, and self-cleaning of the cleaning tool 11 can beexecuted by the suitable self-cleaning member 60. This makes it possibleto perform highly effective self-cleaning of a cleaning tool in a shorttime period.

Note that there is also available an inorganic oxide-based material,such as quartz, in which a hydrogen-bonding component of surface freeenergy as described above decreases significantly with increase intemperature. For this reason, when warming of the liquid 64 is used incombination, a material, such as PMMA, which is an organic polymer-basedmaterial and has a relatively large hydrogen-bonding component even athigh temperatures due to the presence of a polar group in a molecularstructure may be used for a cleaning tool which is intended forprocessing debris having a larger hydrogen-bonding component. In otherwords, the first member 60A may be formed of a material in which surfacefree energy has a larger hydrogen-bonding component and a smallerdispersion force component than the second member 60B at the time ofself-cleaning of the cleaning tool 11.

Fourth Embodiment

A substrate cleaning apparatus 20 according to a fourth embodiment hasthe same configuration as the substrate cleaning apparatus 20 accordingto the third embodiment. The substrate cleaning apparatus 20 accordingto the fourth embodiment is different from the substrate cleaningapparatus 20 according to the third embodiment in that a cleaning tool11 is brought into contact with both a first member 60A and a secondmember 60B.

FIG. 11 is a flowchart showing an example of a self-cleaning process tobe executed by a controller 50 according to the fourth embodiment. Thisprocess is executed when the cleaning tool 11 is self-cleaned. When theself-cleaning process is executed, the controller 50 first executesself-cleaning processing by the first member 60A by bringing thecleaning tool 11 into contact with the first member 60A while rotatingthe cleaning tool 11 (S52). The controller 50 then executesself-cleaning processing by the second member 60B by bringing thecleaning tool 11 into contact with the second member 60B while rotatingthe cleaning tool 11 (S54) and ends the present process.

According to the fourth embodiment, self-cleaning of the cleaning tool11 is executed by bringing the cleaning tool 11 into contact with thefirst member 60A that is formed of an inorganic oxide-based material oran organic polymer-based material having a polar group in a molecularstructure while rotating the cleaning tool 11 and then bringing thecleaning tool 11 into contact with the second member 60B that is formedof an organic polymer-based material having no polar group in amolecular structure while rotating the cleaning tool 11. This makes itpossible to first remove processing debris, such as abrasive grains, inwhich surface free energy has a larger hydrogen-bonding component, fromthe cleaning tool 11 and then remove processing debris, such as organiccomplexes, in which surface free energy has a larger dispersion forcecomponent, from the cleaning tool 11. By this method, highly effectiveself-cleaning of a cleaning tool can be performed in a short timeperiod.

Although the embodiments of the present invention have been describedabove, the above-described embodiments of the invention are intended foreasy understanding of the present invention and are not intended tolimit the present invention. It is apparent that the present inventioncan be changed and altered without departing from the spirit thereof andinclude its equivalents. The embodiments and modifications can bearbitrarily combined in a range where at least a part of theabove-described problems can be solved or a range where at least a partof the effects can be produced. The components described in the claimsand the specification can be arbitrarily combined or omitted.

The present application claims priority from Japanese Patent ApplicationNo. 2018-048217 filed on Mar. 15, 2018. All disclosures including thespecifications, claims, drawings, and abstract of Japanese PatentApplication No. 2018-048217 are incorporated herein by reference in itsentirety. All disclosures including the specifications, claims,drawings, and abstract of Japanese Patent Laid-Open No. 2005-012238(PTL 1) are incorporated herein by reference in its entirety.

REFERENCE SIGNS LIST

-   -   10 substrate processing apparatus    -   11 cleaning tool    -   11A pen member    -   11B roll member    -   20 substrate cleaning apparatus    -   31 rotation mechanism    -   32 holding mechanism    -   40 support member    -   42 supply module    -   50 controller    -   52 input module    -   60 self-cleaning member    -   60A first member (first self-cleaning member)    -   60B second member (second self-cleaning member)    -   62 bath    -   64 liquid    -   65 transport mechanism    -   66 adjustment mechanism    -   67 vibration module    -   68 jetting module

1. A substrate cleaning apparatus comprising: a cleaning tool forcleaning a substrate while in contact with a surface of the substrate; aself-cleaning member for self-cleaning the cleaning tool while incontact with the cleaning tool; a rotation mechanism for rotating thecleaning tool; a holding mechanism which holds the cleaning tool, theholding mechanism being capable of pressing the cleaning tool againstthe substrate and pressing the cleaning tool against the self-cleaningmember; and a controller which controls pressing force for the cleaningtool against the self-cleaning member such that torque, with which therotation mechanism rotates the cleaning tool when the cleaning tool isin contact with the self-cleaning member, is prescribed torque equal toor more than substrate cleaning torque, with which the rotationmechanism rotates the cleaning tool when the cleaning tool cleans thesubstrate.
 2. A substrate cleaning apparatus according to claim 1,wherein the controller, when the cleaning tool is in contact with theself-cleaning member, controls the holding mechanism such that thecleaning tool is pressed against the self-cleaning member with firstpressing force when the cleaning tool is rotating at a first rotationalspeed and controls the holding mechanism such that the cleaning tool ispressed against the self-cleaning member with second pressing forcelarger than the first pressing force when the cleaning tool is rotatingat a second rotational speed higher than the first rotational speed. 3.A substrate cleaning apparatus according to claim 1, wherein thecontroller, when the cleaning tool is in contact with the self-cleaningmember in liquid or with supply of the liquid, controls the holdingmechanism such that the cleaning tool is pressed against theself-cleaning member with first pressing force when the liquid is at afirst temperature and controls the holding mechanism such that thecleaning tool is pressed against the self-cleaning member with secondpressing force larger than the first pressing force when the liquid isat a second temperature higher than the first temperature.
 4. Asubstrate cleaning apparatus comprising: a cleaning tool for cleaning asubstrate while in contact with a surface of the substrate; a firstself-cleaning member for self-cleaning the cleaning tool while incontact with the cleaning tool, the first self-cleaning member beingformed of a first material; and a second self-cleaning member forself-cleaning the cleaning tool while in contact with the cleaning tool,the second self-cleaning member being formed of a second material,wherein the substrate cleaning apparatus selects one of the firstself-cleaning member and the second self-cleaning member on the basis ofexternal input, and self-cleans the cleaning tool by bringing thecleaning tool into contact with the selected self-cleaning member.
 5. Asubstrate cleaning apparatus according to claim 4, wherein thecontroller self-cleans the cleaning tool by bringing the cleaning toolinto contact with the first self-cleaning member and then bringing thecleaning tool into contact with the second self-cleaning member.
 6. Thesubstrate cleaning apparatus according to claim 4, wherein the firstmaterial is a material in which surface free energy has a largerhydrogen-bonding component and a smaller dispersion force component thanthe second material at the time of self-cleaning the cleaning tool. 7.The substrate cleaning apparatus according to claim 4, wherein the firstmaterial is an inorganic oxide-based material or a first organicpolymer-based material which has a polar group in a molecular structure,and the second material is a second organic polymer-based material whichis non-polar.
 8. The substrate cleaning apparatus according to claim 1,wherein the self-cleaning of the cleaning tool comprises short-timeself-cleaning of first duration and long-time self-cleaning of secondduration longer than the first duration, and ultrapure water is used inthe short-time self-cleaning, and an ultrapure water rinse is used afterchemical solution processing or only ultrapure water processing isperformed in the long-time self-cleaning.
 9. The substrate cleaningapparatus according to claim 1, further comprising: a bath in whichliquid is stored and which houses the self-cleaning member; and avibration module which gives ultrasound vibration to the liquid.
 10. Thesubstrate cleaning apparatus according to claim 1, further comprising ajetting module which jets gas or liquid toward the cleaning tool whenthe cleaning tool is self-cleaned.
 11. A substrate cleaning methodcomprising: a cleaning step of cleaning a substrate by rotating acleaning tool and bringing the cleaning tool into contact with a surfaceof the substrate; and a self-cleaning step of self-cleaning the cleaningtool by rotating the cleaning tool and bringing the cleaning tool intocontact with a self-cleaning member, wherein the self-cleaning stepcomprises controlling pressing force for the cleaning tool against theself-cleaning member such that torque which rotates the cleaning tool isprescribed torque equal to or more than substrate cleaning torque whichrotates the cleaning tool in the cleaning step.
 12. A substrate cleaningmethod according to claim 11, wherein the self-cleaning step comprisespressing the cleaning tool against the self-cleaning member with firstpressing force when the cleaning tool is rotating at a first rotationalspeed and pressing the cleaning tool against the self-cleaning memberwith second pressing force larger than the first pressing force when thecleaning tool is rotating at a second rotational speed higher than thefirst rotational speed.
 13. A substrate cleaning method according toclaim 11, wherein the self-cleaning step comprises pressing the cleaningtool against the self-cleaning member with first pressing force when theliquid is at a first temperature and pressing the cleaning tool againstthe self-cleaning member with second pressing force larger than thefirst pressing force when the liquid is at a second temperature higherthan the first temperature.
 14. A substrate cleaning method comprising:a cleaning step of cleaning a substrate by rotating a cleaning tool andbringing the cleaning tool into contact with a surface of the substrate;a selection step of selecting one of a first self-cleaning member whichis formed of a first material and a second self-cleaning member which isformed of a second material, on the basis of external input; and aself-cleaning step of self-cleaning the cleaning tool by rotating thecleaning tool and bringing the cleaning tool into contact with theself-cleaning member selected in the selection step.
 15. A substratecleaning method according to claim 14, wherein the self-cleaning stepcomprises a first self-cleaning step of self-cleaning the cleaning toolby rotating the cleaning tool and bringing the cleaning tool intocontact with a first self-cleaning member which is formed of a firstmaterial; and a second self-cleaning step of, after the firstself-cleaning step, self-cleaning the cleaning tool by rotating thecleaning tool and bringing the cleaning tool into contact with a secondself-cleaning member which is formed of a second material.